Insulin glargine is a long-acting insulin preparation that can be used for initial treatment and long-term management of diabetes mellitus， especially in cats. Glargine is recommended as a first-choice insulin in newly diagnosed diabetic cats. Intermediate-acting insulins (eg， porcine insulin zinc [ie， lente]， neutral protamine Hagedorn [NPH]) are considered first-choice insulin therapies in dogs with uncomplicated diabetes mellitus; however， glargine can also be considered if these insulins do not have a long enough duration of activity.

Adverse effects of insulin therapy may include hypoglycemia， hypokalemia， hypophosphatemia (DKA only)， insulin-induced rebound hyperglycemia (ie， Somogyi effect)， insulin antagonism and resistance， rapid insulin metabolism， weight gain， and local or allergic reactions to the “foreign” proteins.

Because there are no alternatives for insulin when it is used for diabetic indications， there are no absolute contraindications to its use except during episodes of hypoglycemia. If animals develop hypersensitivity (local or otherwise) or if insulin resistance develops， a change in type or species source (eg， human， bovine， porcine) of insulin should be considered after other etiologies for poor control (eg， expired insulin， concurrent disease or medication interference) have been ruled out. Patients presented with severe ketoacidosis， anorexia， lethargy， and/or vomiting should be treated with short-acting insulin (eg， regular) and appropriate supportive therapy until their condition is stabilized. Insulin glargine is a U-100 strength insulin. It is crucial for patient safety to only use U-100 syringes when measuring and administering U-100 insulin.

Insulin is used for the treatment of diabetes mellitus. Regular insulin is commonly used for stabilization of the diabetic pet and is the only formulation labeled for intravenous administration (IV); it is also administered by intramuscular (IM) and subcutaneous (SC) injection.